Apparatus for depositing powdered substance on the inner surface of inflation tube

ABSTRACT

An apparatus for uniformly and thinly depositing finely powdered substance on the inner surface of an inflation tube, which is being shaped by an ascensional inflation method, by diffusing said powdered substance into gaseous atmosphere in the inflation tube by means of static electricity.

United States Patent 1 Saito [451 Aug. 7, 1973 APPARATUS FOR DEPOSITINGPOWDERED SUBSTANCE ON THE INNER SURFACE OF INFLATION TUBE [75] Inventor:

[73] Assignee: Nikka Kabushiki Kaisha, Tokyo,

Japan [22] Filed: Nov. 9, 1971 [211 App]. No.: 197,087

Shiro Saito, Tokyo, Japan [52] US. Cl 239/15, 18/14 H, 118/44, 118/622[51] Int. Cl 1305b 5/02 [58] Field of Search 239/15; 118/44, 622; 1425/95; 18/14 H [56] References Cited UNITED STATES PATENTS Schanz425/95 x- 3,125,457 3/1964 Meister 118/622 X 3,417,453 12/1968 Clarke118/622 UX 3,474,755 10/1969 V00 118/44 3,323,489 6/1967 Gustin...118/622 X FOREIGN PATENTS OR APPLICATIONS 241,422 11/1962 Australia118/622 Primary ExaminerM. Henson Wood, Jr. Assistant ExaminerMichae1Mar Attorney-Richards & Geier [57] ABSTRACT An apparatus for uniformlyand thinly depositing finely powdered substance on the inner surface ofan inflation tube, which is being shaped by an ascensional inflationmethod, by diffusing said powdered substance into gaseous atmosphere inthe inflation tube by means of static electricity.

7 Claims, 3 Drawing Figures PMEMED 7373 3, 750. 948

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G LM 4 5W ATTQ mu E35 APPARATUS FOR DEPOSITING POWDERED SUBSTANCE ON THEINNER SURFACE OF INFLATION TUBE BACKGROUND OF THE INVENTION Thisinvention relates to an apparatus for uniformly depositing finelypowdered substance on the inner surface of an inflation tube.

In general, in the continuous synthetic resin tube shaping process,particularly when an inflation method is employed, a tube such as forexample a polyethylene tube extruded out in the form of a tube from anannular slit in the die is inflated with blowing air. At the same timethe tube is cooled from the outside and held between pinch rolls, andthe thus folded tube-shaped film lamination is taken up on a winderthrough a guide roll. In some cases, however, the two film sheets facingeach other may be tightly stuck together for some reason or other, thiscausing great impediment to the succeeding operations.

Such impediment would be eliminated if finely powdered substance couldbe uniformly deposited over the inner surface of a sealed inflation-tubeformed between the die and the pinch roll. l

However, admitted that the finely powdered substance could be introducedabove the die by some mechanical means, it is extremely difficult tohave these powdered substance uniformly deposited on the entire innersurface of the tube since the tube usually has inner diameter as largeas 1 meter or more and also since a convection formed from an upwardcurrent in the central part and a downward current in the peripheralpart is present in the interior of the inflation tube as the dietemperature is usually as high as 200C and the inflation tube is cooledfrom the outside. If the internal pressure of the inflation tube is notkept constant, the finished tube diameter may be varied, so that it ispractically impossible to diffuse the finely powdered substanceparticles by using compressed air. The fact that the amount of suchfinely powdered substance to be deposited, although somewhat variedaccording to the purpose of use, is usually as small as about 0.15g/m isan additional factor that increases the diff:- culties.

SUMMARY OF THE INVENTION The present invention has eliminated the abovementioned conventional difficulties for diffusing the finely powderedsubstance by using an electro-static means.

An object of the present invention is to provide a new and improvedapparatus for depositing finely powdered substance on the inner surfaceof an inflation tube.

Another object of the present invention is to provide an apparatus fordepositing finely powdered substance uniformly and thinly over theentire inner surface of an inflation tube by diffusing said powderedsubstance by means of static electricity and fluctuation of saidpowdered substance. According to the present invention, an annularmember made of an insulating material is mounted at the end of atransporting tube which transports the finely powdered substance. Thetransporting tube passes through and extends uprightly above anascensional inflation die along with a high tension cable electricallyconnected toa high voltage generator. A high voltage electrode member issecured externally at the top of said annular memberand is applied witha high voltage of opposite polarity to that of the electric charge onthe inflation tube by said high tension cable. Within said transportingtube is provided a flexible screw. Further, inside of said annularmember, a rotary cutter means for breaking upthe mass of the powderedsubstance which may have been formed during transportation may bemounted at an end of said flexible screw.

' A complete understanding of the invention may be obtained from thefollowing detailed description of an apparatus constituting a specificembodiment thereof, when read in conjunction with the appended drawings,in which:

FIG. 1 is an illustration showing the entire mechanism of the apparatusaccording to the present inventron;

FIG. 2 is a sectional view of the essential parts of the apparatus, and

FIG. 3 is a plane view of the essential parts of the apparatus.

PREFERRED EMBODIMENT OFTHE INVENTION Referring first to FIG. 1, there isshown an ascerb sional inflation die, generally designated by numeral 1,which is of a' known type. Molten synthetic resin is introduced througha coupling tube 2 connected to an extruder (not shown), then passedthrough apassage 4 formed along the peripheral wall of a mandrel 3 andfinally forced out through an annular slit 5 to form an inflationtube, 6of thin film. The diameter of the tube 6 is determined according to theamount of air blown in from a hole 7. Although not shown,thetube iscooled with air from a cooling ring, then held between squeeze rools andfinally taken up on a winder. These operations are quite similar tothose employed in the conventional devices. I

The mandrel 3 has formed therein the through-holes 8 and 9 through whichare,passed, respectively, a high tension cable 11 electrically connectedto a high voltage generator 10 and a transporting tube 13 made ofametal, such as copper, connected to a feeder 12 of finely powderedsubstance. At the bottom ends of said holes'8 and'9, the plugs 14 and 15are threadedly fixed respectively. The portion of the transporting tube13 that extends within the mandrel 3 is provided with a cooling jacket17. A coolant is introduced from an inlet tube 16 of said cooling jacket17 and passes through the jacket into an outlet tube 18. r i

The high voltage generator 10 may, for instance, be a full-wave, voltagedoubler rectification type generator having rated input voltage of 100 Vand output voltage of DC BOKV. The polarity of the output voltage can beoptionally switched with ease. The high tension cable 11 is coated withan insulating layer of silicon rubber and is braided with glass biberoutside thereof. The feeder 12 includes a flexible screw 20 which isarranged to be rotated by a DC motor 21 and which is disposed in atransporting tube 13 for transferring the powdered substance in a tank19 through said transporting tube 13. The number of rotations of saidflexible screw can be adjusted by a controller 22. The flexicorn starchand white potato starch grains having their surfaces coated with siliconresin. The grain size is preferably about The metal-made transportingtube 13, which passes through and extends upright above the die 1, iselectrically earthed and has mounted at its top end an annular member 24made of an insulating material such as for example tetrafluoroethylene.As apparent in FIG. 2, the annular member 24 has formed therein threestepped holes, i.e., a lower hole 25, a middle hole 26 and an upper hole27, and a tapered opening 28 extending upwardly from the end of theupper hole 27. In said middle holes 26 and upper hole 27 is fitted abrassmade receiving member 29, a tapped hole of which is threadedlyengaged with the threaded end portion of the transporting tube 13inserted through the lower hole 25. The bottom of the annular member 24is pressed by a nut 30 which is threadedly engaged with the threadedportion of the transporting tube 13, thereby fixing said annular memberin position.

A high voltage electrode member 31 made of brass is mounted over theexternal upper annular portion and around the external uppercircumferencial portion of the annular member. An upper innercircumferential portion 37 of the electrode member extends verticallyfrom'the upper end of the inner surface of the tapered opening 28. Theannular member 24 and the high voltage electrode member 31 are fastenedtogether by a machine screw 32 which also secures an end of the hightension cable 1 1 so as to impress a high voltage thereto.

A brass-made rotor 33 is mounted at the end of the flexible screw 20. Aboss 34 of said rotor 33 is smaller in diameter than the central hole ofthe receiving member 29 in which said boss is inserted, so that anannular space 35 is formed therearound and hence the powdered substancetransferred here through the transporting tube 13 by the flexible screw20 may be exposed to the outside by passing through this space 35. Asapparent'in FIG. 3, the rotor 33 is provided with six pieces of cutterblades 36 which are freely rotatable on the upper surface of thereceiving member 29 to break up the powdered substance transferred herein the form of masses.

Now, the operation of the present apparatus is described. First, aninflation tube 6 is shaped according to a known inflation method andthen the high voltage generator 10 is adjusted such as to apply to thehigh voltage electrode 31 a high voltage of about 30,000 KV in case thetube diameter is less than 1 meter and about 50,000 to 80,000 KV if thetube diameter is larger than that. The electric voltage applied is of apolarity opposite to that of the static electricity (negative in manycases) of the inflation tube 6. Then, a coolant is passed through thejacket 17 and the DC motor 21 is operated to feed the powdery substancein the tank 19 upwardly of the rotor 33 through the transporting tube13. The fine solid particles of the powdered substance broken up by therotating cutter blades 36 are attracted by and fly toward the innercircumferential portions 37 of the high voltage electrode member 31, andupon contacting said inner circumferential portion 37 of the electrodemember 31 the particles are charged with the same polarity as saidelectrode member 31. The charged particles repulse each other and arediffused by producing fluctuation. The electrode member 31 is positionedalmost in the center of the inflation tube so that the charged particlesdiffused from the electrode member can be riden on the ascending currentof the convection in the inflation tube 6.

Thus, the fine solid particles of the powdered substance charged with apolarity opposite to that of the electric charge on the inflation tubecan be uniformly deposited on the inner surface of the tube owing to theelectrostatic attractive force irrespective of the convection in theinflation tube. Needless to say, there does not take place any leakageof the finely powdered substance diffused in the interior of theinflation tube which is sealed by the die and the squeeze rolls.

The cylindrical portion of the high voltage electrode member 31 coveringaround the external upper circumferential portion of the annular member24 serves to radially repulse the particles of the powdered substancewhich tend to pass near said cylindrical portion while precipitating.This means is advantageous for reducing the amount of wasteful sprayedparticles which are deposited on the external surface of thetransporting tube 13 which acts as an earthing electrode, or accumulatedon the die 1.

The present invention is not limited to the above mentioned embodimentbut can be variously modified without departing from the spirit ofthepresent invention.

What is' claimed is:

1. An apparatus for depositing finely powdered substance on the innersurface of an inflation tube, which comprises a high tension cableelectricallyv connected to a high. voltage generator; a transportingtubcfor transfering said powdered substance from a feeder, saidtransporting tube passing through and extending uprightly above anascensional inflation die along with said high tension cable and beingearthed electrically, within said transporting tube a flexible screwbeing disposed for rotatable conveying said powdered substance; anannular member made of an insulating material and mounted at an end ofsaid transporting tube; and a high voltage electrode member securedexternally at the top of said annular member and applied with a highvoltage of a polarity opposite to that of the charge on the inflationtube by said high tension cable.

2. An apparatus as defined in claim 1, wherein said high tension cableis coated with an insulating layer of silicon rubber and is braided withglassfiber outside thereof.

3. An apparatus as defined in claim 1, wherein said high tension cableand said transporting tube are passed through two through-holes whichare formed uprightly within the ascensional inflation die, at the bottomend of each hole a plug being fixed threadedly, the portion of saidtransporting tube that extends within the inflation die being providedwith a cooling jacket.

4. An apparatus asdefined in claim 1, wherein said flexible screwdisposed within the transporting tube is made a bundle of plural piecesof steel wires on which another steel wire is spirally coiled at asuitable pitch.

5. An apparatus as defined in claim 1, wherein said high voltageelectrode member is made of brass and is mounted over the external upperannular portion and around the external upper circumferential portion ofthe annular member.

6. An apparatusas defined in claim 1, wherein said annular member formstherein a lower hole, a middle hole, an upper hole and a taperedopening, said three holes becoming larger in steps such that said upperhole is the largest, said tapered opening extending upwardly from theend of said upper hole, a brass-made receiving member being fitted insaid middle hole and said upper hole, said receiving member beingtherein provided with a tapped hole which is threadedly engaged with thethreaded end portion of the transporting tube inserted through the lowerhole, the bottom of said annular member being pressed by a nut which isthreadedly engaged with a threaded portion of the transporting tube.

7. An apparatus as defined in claim 6, wherein said receiving memberforms therein a central hole in which receiving member in which saidboss is inserted.

* i III t

1. An apparatus for depositing finely powdered substance on the innersurface of an inflation tube, which comprises a high tension cableelectrically connected to a high voltage generator; a transporting tubefor transfering said powdered substance from a feeder, said transportingtube passing through and extending uprightly above an ascensionalinflation die along with said high tension cable and being earthedelectrically, within said transporting tube a flexible screw beingdisposed for rotatable conveying said powdered substance; an annularmember made of an insulating material and mounted at an end of saidtransporting tube; and a high voltage electrode member securedexternally at the top of said annular member and applied with a highvoltage of a polarity opposite to that of the charge on the inflationtube by said high tension cable.
 2. An apparatus as defined in claim 1,wherein said high tension cable is coated with an insulating layer ofsilicon rubber and is braided with glassfiber outside thereof.
 3. Anapparatus as defined in claim 1, wherein said high tension cable andsaid transporting tube are passed through two through-holes which areformed uprightly within the ascensional inflation die, at the bottom endof each hole a plug being fixed threadedly, the portion of saidtransporting tube that extends within the inflation die being providedwith a cooling jacket.
 4. An apparatus as defined in claim 1, whereinsaid flexible screw disposed within the transporting tube is made abundle of plural pieces of steel wires on which another steel wire isspirally coiled at a suitable pitch.
 5. An apparatus as defined in claim1, wherein said high voltage electrode member is made of brass and ismounted over the external upper annular portion and around the externalupper circumferential portion of the annular member.
 6. An apparatus asdefined in claim 1, wherein said annular member forms therein a lowerhole, a middle hole, an upper hole and a tapered opening, said threeholes becoming larger in steps such that said upper hole is the largest,said tapered opening extending upwardly from the end of said upper hole,a brass-made receiving member being fitted in said middle hole and saidupper hole, said receiving member being therein provided with a tappedhole which is threadedly engaged with the threaded end portion of thetransporting tube inserted through the lower hole, the bottom of saidannular member being pressed by a nut which is threadedly engaged with athreaded portion of the transporting tube.
 7. An apparatus as defined inclaim 6, wherein said receiving member forms therein a central hole inwhich a rotary cutter means for breaking up the masses of the powderedsubstance which may have been formed during transportation is received,said rotary cutter means comprising a plurality of cutter blades and aboss, said cutter blades extending radially from said boss mounted atthe end of the flexible screw disposed within the transporting tube andbeing freely rotatable on the upper surface of the receiving member,said boss being smaller in diameter than said central hole of thereceiving member in which said boss is inserted.